题目传送门
1 /*
2 题意：删除若干行，使得n行字符串成递增排序
3 暴力+构造：从前往后枚举列，当之前的顺序已经正确时，之后就不用考虑了，这样删列最小
4 */
5 /************************************************
6 Author :Running_Time
7 Created Time :2015-8-3 10:49:53
8 File Name :C.cpp
9 *************************************************/
10
11 #include <cstdio>
12 #include <algorithm>
13 #include <iostream>
14 #include <sstream>
15 #include <cstring>
16 #include <cmath>
17 #include <string>
18 #include <vector>
19 #include <queue>
20 #include <deque>
21 #include <stack>
22 #include <list>
23 #include <map>
24 #include <set>
25 #include <bitset>
26 #include <cstdlib>
27 #include <ctime>
28 using namespace std;
29
30 #define lson l, mid, rt << 1
31 #define rson mid + 1, r, rt << 1 | 1
32 typedef long long ll;
33 const int MAXN = 1e2 + 10;
34 const int INF = 0x3f3f3f3f;
35 const int MOD = 1e9 + 7;
36 char s[MAXN][MAXN];
37 int n, m;
38 bool ok[MAXN][MAXN];
39
40 int main(void) { //Codeforces Round #283 (Div. 2) C. Removing Columns
41 while (scanf ("%d%d", &n, &m) == 2) {
42 for (int i=1; i<=n; ++i) {
43 scanf ("%s", s[i] + 1);
44 }
45 int ans = 0; memset (ok, false, sizeof (ok));
46 bool flag = true;
47 for (int j=1; j<=m; ++j) {
48 flag = true;
49 for (int i=2; i<=n; ++i) {
50 if (ok[i][i-1]) continue;
51 if (s[i][j] < s[i-1][j]) {
52 ans++; flag = false; break;
53 }
54 }
55 if (flag) {
56 for (int k=2; k<=n; ++k) {
57 if (s[k][j] > s[k-1][j]) ok[k][k-1] = true;
58 }
59 }
60 }
61 printf ("%d
", ans);
62 }
63
64 return 0;
65 }